This invention relates to stabilizers for the rear axle of a vehicle and in particular to such stabilizers as are designed to provide uniform vehicle self-steering tendencies over a wide range of vehicle loads.
Increased loading on a motor vehicle, particularly one equipped with a front mounted engine, tends to be distributed more on the rear axle of the vehicle than on the front axle. There is consequently a large change in the vehicle load forces on the rear wheels compared to those on the front wheels. As a result of this differential change in wheel loading, there is, when the vehicle negotiates a curve, a large increase in the skew angle of the rear wheels, or of the rear axle respectively, and only a small increase in the skew angle of the front wheels, or of the front axle respectively, because the skew angle depends, as is well known, on the load forces on the wheels. Skew angle is the angle between the plane of the wheel and the direction of the wheel travel. It is also well known that the self-steering characteristic of a vehicle depends on the difference between the skew angle of the rear axle and the skew angle of the front axle. Accordingly, a change of the self-steering characteristic takes place when the vehicle is loaded. A vehicle with a neutral self-steering characteristic when empty becomes over-steering when loaded. Similar changes occur in a vehicle which is under-steering when empty, in that it tends to become neutral or even over-steering when loaded. Such changes in self-steering tendency are naturally undesired.
In order to avoid load dependent changes in self-steering tendency it is desirable to provide a stabilizer for correcting the changes in skew angle. This may be achieved by adjusting the roll restoring moment exerted by the suspension between the rear axle and the chassis in such a manner it decreases with increasing vehicle load.
In doing so the change in rear wheel loading of the fully loaded vehicle (increased load on the curve outer wheel and decreased load on the curve inner wheel) when negotiating a curve will be smaller with respect to conventionally stabilized vehicles and consequently there will be a smaller skew angle of the rear axle. If the rolling restoring moment on the rear axle is decreased with increasing vehicle load, the roll angle of the vehicle will also increase and consequently there will be exerted a greater roll restoring moment on the front axle so that the skew angle of the front axle will increase with respect to conventionally stabilized vehicles. This decrease of the skew angle of the rear axle and the simultaneous increase of the skew angle of the front axle with increasing vehicle load reduces the tendency of over-steering of the fully loaded vehicle and makes the self-steering characteristics substantially load independent.